1. Field of the Invention
The invention relates generally to magnetic disk drives and more specifically to high density removable media used in computer systems.
2. Description of the Prior Art
Continual advances in floppy disk technology have allowed tile rapid migration from eight inch, to 5.25 inch to 3.5 inch diskettes. Originally, 5.25 inch diskettes held only 360 K bytes of data, but higher track and more efficient recording formats have allowed the smaller 3.5 inch diskette to store as much as 1.44 M bytes in the recent high density (HD) format. Such rapid migration has caused severe interoperability concerns, because of the physical incompatibility between the traditional formats. The recent HD format is a ray of hope that time situation will improve, in that both Apple Macintosh IIs and IBM-PCs equipped with HD drives record in basically an interchangeable format.
Advances in floppy disk technology have not stayed still. By embedding optical servo information in an otherwise standard 3.5 inch micro-floppy diskette, storage capacities of twenty megabytes and beyond are possible. The Micro Standards Committee, sponsored by the Microcomputer Managers Association, announced at COMDEX/Spring 1989 a 10-month study of proposed new formats to replace the aging 1.44 M byte diskette. (See, "Draft White Paper on a New Standard for Very-High-Density Diskette Drives," Feb. 5, 1990, published by the Micro Standards Committee, 50 W. 34th St., Suite 23C7, New York, N.Y. 10001.) The result was to recommend a 20.9 M byte optical-magnetic format that was judged to be superior on every criterion rated.
In the prior art, only two devices have been used on diskettes to signal to a drive special properties of the diskette. Both have been mechanical. The original eight inch floppy disks had a notch in the jacket that was covered to prohibit writing on the disk. Some diskettes have a mechanical switch that allows/prohibits writing. The latest HD micro-floppy diskettes have a hole to differentiate them to the disk drive from earlier 400 K byte (Apple), 722 K byte (IBM), or 800 K byte (Apple) 3.5 inch diskettes. The 2.88 M byte industry format has a capacity hole in yet a different location than the 1.44 M byte diskette. To guard against improper formatting a drive should have three switches, one for write protect and two to detect capacity. Other than that, the prior art has not placed any information on the recording surface of a diskette to allow the disk drive to auto-configure itself to the particular diskette inserted.